This document discusses Caterpillar's journey to meet increasingly stringent EPA emissions standards. It outlines the Tier 4 emissions limits and timeline for non-road engines between 19-560kW, and describes the technologies used in Caterpillar engines like SCR, DPF, and DOC to reduce emissions of NOx and particulate matter to meet Tier 4 Final requirements. These systems are designed to be transparent to the operator with maintenance intervals of thousands of hours.